lkml.org 
[lkml]   [2018]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 05/10] staging: erofs: add a full barrier in erofs_workgroup_unfreeze
From
Date
Hi Andrea,

On 2018/11/23 17:51, Andrea Parri wrote:
> Correct. This is informally documented in Documentation/atomic_t.txt
> and formalized within tools/memory-model/.
>
>
>> I don't know whether my understanding is correct, If I am wrong..please correct me, or
>> I need to add more detailed code comments to explain in the code?
> Yes, please; please review the above points (including 1. and 3.) and
> try to address them with inline comments. Maybe (if that matches the
> *behavior*/guarantee you have in mind...) something like:
>
> [in erofs_workgroup_unfreeze()]
>
> /*
> * Orders the store/load to/from [???] and the store to
> * ->refcount performed by the atomic_set() below.
> *
> * Matches the atomic_cmpxchg() in erofs_workgroup_get().
> *
> * Guarantees that if a successful atomic_cmpxchg() reads
> * the value stored by the atomic_set() then [???].
> */
> smp_mb();
> atomic_set(&grp->refcount, v);
>
>
> [in erofs_workgroup_get()]
>
> /*
> * Orders the load from ->refcount performed by the
> * atomic_cmpxchg() below and the store/load [???].
> *
> * See the comment for the smp_mb() in
> * erofs_workgroup_unfreeze().
> */
> if (unlikely(atomic_cmpxchg(&grp->refcount, o, o + 1) != o))
> goto repeat;
>

OK, I will add these comments in the next version patchset, will be sent later.
Thanks for your suggestion. :)

Thanks,
Gao Xiang

> Thanks,
> Andrea
>
>

\
 
 \ /
  Last update: 2018-11-23 11:00    [W:0.048 / U:19.960 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site